Washington (CNN) -- The U.S. military has inadequate and outdated defenses against internal threats, Defense Secretary Robert Gates said Friday after reviewing a Pentagon report examining the Fort Hood shooting last year.

Gates, who announced the findings of the report at a news conference, said the department has not done enough to adapt to the evolving domestic internal security threat to American troops and military facilities.

As well as failing to communicate internal threats to the security of personnel, he said there was a lack of supervision over Army Maj. Nidal Malik Hasan, the psychiatrist now charged with killing 13 people and wounding 28.

Gates said the report also makes "accountability recommendations" for Army personnel who supervised Hasan.

He said its recommendations will be sent to the secretary of the Army for review. He said he is also directing the assistant secretary of defense for homeland defense, Paul Stockton, to look at how the military can communicate more clearly internal threats in order to improve the security of military personnel.

"It is clear that, as a department, we have not done enough to adapt to the evolving domestic internal security threat to American troops and military facilities that has emerged over the past decade," Gates said.

In a written statement, the FBI said it had identified four areas where change was needed:

• Better information sharing between the FBI and the Department of Defense regarding FBI investigations of military personnel;

• More redundancy in the review process to limit the risk of human error;

• Improvements in information technology to beef up agents' and analysts' ability to sift through information;

• Better training for members of joint terrorism task forces.

A Department of Defense review will probably identify other areas "that can be strengthened," it said.

In a written statement, Homeland Security and Governmental Affairs Committee Chairman Sen. Joe Lieberman, I-Connecticut, and Susan Collins, R-Maine, the ranking member of the committee, said the report does not adequately address the threat posed by violent Islamist extremism to the military.

Lieberman added, "I believe firmly that if DoD educates its personnel about violent Islamist extremism -- and how terrorists distort the Islamic faith to promote violence -- we will increase trust between the thousands of Muslim-Americans serving honorably in the military and their colleagues."

He said the omission underscores the need for their committee's investigation.

And he accused the Department of Defense of having been "less than forthcoming" in giving his committee access to documents and witnesses.